Generally display devices such as Liquid Crystal Displays (LCD) used in electronic equipment require high voltage for permitting its operation in a wide range of temperatures. For example, according to technical standards of radio telephones, the radio telephone including its LCD must operate in a temperature range from -30.degree. C. to +60.degree. C. having a voltage difference of 9 v (e.g., -4 v to +5 v).
On the other hand, logic circuitry employed in such electronic equipment usually operates at a fixed voltage of approximately 5 volts. That is, zero voltages for logical "0" and 5 volts for logical "1". Therefore, incorporating logic circuitry and a driver for an LCD display device, it is necessary to provide a negative voltage generator. which produces a wider range of voltages from +5 volts for the logic circuitry to a negative potential for providing the requisite voltage difference for the LCD.
A conventional negative voltage generator is shown in FIG. 1. The negative voltage generator comprises a negative voltage generation circuit 101 and a voltage regulator circuit 102. The voltage (5 volts) from a power source (not shown) is applied to negative voltage generation circuit 101, voltage regulator circuit 102, and load 103.
The negative voltage generation circuit 101 comprises a non-stable multivibrator circuit 104 and a voltage multiplier circuit 105. A complementary metal-oxide semiconductor (CMOS) device 106 is employed in the non-stable multivibrator circuit 104 for generating an oscillation pulse signal having a high voltage level of 5 volts and a low voltage level of 0 volts. The purse signal is applied to the voltage multiplier circuit 105. Voltage multiplier circuit 105 produces a signal which is inversely multiplied; that is, a high voltage level of approximately 0 volts and a low voltage of approximately -4 volts are provided in accordance with the applied pusle signal. This signal is applied to an operational amplifier 107 in voltage regulator circuit 102. Voltage regulator circuit 102 outputs a stabilized signal having a voltage, for example, of -4 volts, which is applied to load 103. Therefore, any voltage level from +5 volts to -4 volts is readily available for the LCD load 103.
A drawback of the prior art is that the use of certain semiconductor devices, such as CMOS and FET devices, for the voltage pulse generator result in power dissipation when the device changes states. The larger of the fixed bias voltage applied, the greater the dissipation during switching. Since an LCD circuit requires a particular operational voltage difference, as discussed above, a lower fixed bias voltage cannot be supplied to the semiconductor device in the prior art circuit.